Since he had a great desire to dedicate himself to the American missions, he was sent to the United States when still a seminarian. He was ordained in New York in 1836, and worked for four years for the German immigrants near Buffalo. In 1840, he entered the Redemptorist Congregation and became a traveling preacher.
After his appointment as Bishop of Philadelphia, he established new seminaries, churches and schools. Each year he visited his parishes and mission stations, displaying his pastoral concern for the spiritual welfare of his people. Worn out with his labours Neumann died in 1860.